Buggy code:
public abstract class AbstractExpression { private InstElement leftVertex ; private InstElement rightVertex ; private String leftAttributeName ; private String rightAttributeName ; private AbstractExpression leftSubExpression ; private AbstractExpression rightSubExpression ; private BooleanExpression leftBooleanExpression ; private BooleanExpression rightBooleanExpression ; private NumericExpression leftNumericExpression ; private NumericExpression rightNumericExpression ; protected String operation ; protected List < ExpressionVertexType > expressionVertexTypes ; protected List < String > expressionConnectors ; public AbstractExpression ( InstElement left , InstElement right , String leftAttributeName , String rightAttributeName ) { } public AbstractExpression ( InstElement vertex , String attributeName , boolean replaceTarget , AbstractExpression subExpression ) { } public AbstractExpression ( InstElement vertex , String attributeName , boolean replaceTarget , BooleanExpression booleanExpression ) { } public AbstractExpression ( InstElement vertex , String attributeName , boolean replaceTarget , NumericExpression numericExpression ) { } public AbstractExpression ( AbstractExpression leftSubExpression , AbstractExpression rightSubExpression ) { } public AbstractExpression ( ) { } public AbstractExpression ( InstElement vertex , String attributeName ) { } public Map < String , Identifier > getIdentifiers ( HlclFactory f ) { } private void updateDomain ( AbstractAttribute attribute , InstElement instVertex , Identifier identifier ) { if ( ( attribute . getName ( ) . equals ( "SDReqLevel" ) ) || ( attribute . getName ( ) . equals ( "ClaimExpLevel" ) ) ) { String configdomain = "" ; Set < Integer > values = new HashSet < Integer > ( ) ; for ( InstElement relation : instVertex . getSourceRelations ( ) ) { values . add ( ( ( InstPairwiseRelation ) ( relation ) ) . getInstAttribute ( VAR_LEVEL ) . getAsInteger ( ) ) ; } if ( ( values . size ( ) ) == 0 ) { values . add ( new Integer ( 0 ) ) ; } for ( Integer value : values ) { configdomain += ( value . toString ( ) ) + "," ; } configdomain = configdomain . substring ( 0 , ( ( configdomain . length ( ) ) - 1 ) ) ; identifier . setDomain ( DomainParser . parseDomain ( configdomain ) ) ; } else if ( attribute . getName ( ) . equals ( VAR_VARIABLECONFIGVALUE ) ) { String configdomain = ( ( String ) ( instVertex . getInstAttribute ( VAR_VARIABLECONFIGDOMAIN ) . getValue ( ) ) ) ; <START_BUG> if ( configdomain != null ) <END_BUG> identifier . setDomain ( DomainParser . parseDomain ( configdomain ) ) ; } else if ( attribute . getName ( ) . equals ( VAR_VALUE ) ) { String type = ( ( String ) ( instVertex . getInstAttribute ( VAR_VARIABLETYPE ) . getValue ( ) ) ) ; if ( type . equals ( "Integer" ) ) { String domain = ( ( String ) ( instVertex . getInstAttribute ( VAR_VARIABLEDOMAIN ) . getValue ( ) ) ) ; identifier . setDomain ( DomainParser . parseDomain ( domain ) ) ; } else if ( type . equals ( "Enumeration" ) ) { Object object = instVertex . getInstAttribute ( "enumerationType" ) . getValueObject ( ) ; String domain = "" ; if ( object != null ) { @ SuppressWarnings ( "unchecked" ) Collection < InstAttribute > values = ( ( Collection < InstAttribute > ) ( ( ( InstAttribute ) ( ( ( com . variamos . perspsupport . instancesupport . InstEnumeration ) ( object ) ) . getInstAttribute ( MetaEnumeration . VAR_METAENUMVALUE ) ) ) . getValue ( ) ) ) ; for ( InstAttribute value : values ) { String [ ] split = ( ( String ) ( value . getValue ( ) ) ) . split ( "-" ) ; domain += ( split [ 0 ] ) + "," ; } } domain = domain . substring ( 0 , ( ( domain . length ( ) ) - 1 ) ) ; identifier . setDomain ( DomainParser . parseDomain ( domain ) ) ; } } else if ( ( attribute . getType ( ) . equals ( "Integer" ) ) || ( attribute . getType ( ) . equals ( "Enumeration" ) ) ) { if ( ( attribute . getDomain ( ) ) != null ) identifier . setDomain ( attribute . getDomain ( ) ) ; } } public InstElement getLeft ( ) { } public InstElement getRight ( ) { } public InstElement getLeftVertex ( ) { } public InstElement getRightVertex ( ) { } public String getLeftAttributeName ( ) { } public String getRightAttributeName ( ) { } public AbstractExpression getLeftSubExpression ( ) { } public AbstractExpression getRightSubExpression ( ) { } public Expression getLeftComparativeExpression ( ) { } public Expression getRightComparativeExpression ( ) { } public List < ExpressionVertexType > getExpressionVertexTypes ( ) { } public List < String > getExpressionConnectors ( ) { } public BooleanExpression getLeftBooleanExpression ( ) { } public BooleanExpression getRightBooleanExpression ( ) { } public NumericExpression getLeftNumericExpression ( ) { } public NumericExpression getRightNumericExpression ( ) { } public String getOperation ( ) { } public String expressionStructure ( ) { } protected List < Expression > expressionTerms ( HlclFactory f , Map < String , Identifier > idMap ) { } protected List < Expression > expressionTermsNegation ( HlclFactory f , Map < String , Identifier > idMap , boolean negateLeft , boolean negateRight ) { } public abstract Expression transform ( HlclFactory hlclFactory , Map < String , Identifier > idMap ) { } }

Fix:
if ( ( configdomain != null ) && ( ! ( configdomain . equals ( "" ) ) ) )